In one type of pet toilet described in French Pat. No. 2,247,585 it is possible to spray a wash liquid over the walls and floor of a toilet chamber by pressing a flush button, after of course closing an entrance door to the chamber. Such a system requires that the pet owner take the necessary steps to eliminate any animal waste and, while such manual operation makes the equipment simple and cheap, this arrangement is not good for long-term untended use.
In the system of U.S. Pat. Nos. 2,204,416 and 3,318,285 there is a special door or floor trip that the animal operates to set off the flushing operation. Such arrangements do not do anything more than a simple timed flush of the equipment, and are frequently set off when not necessary, as when for example the animal is merely visiting the box without actually excreting. Moreover such arrangements have such a simple automatic operation that they can be set off while the animal is still inside, or can be set off continuously by a playful pet.